A solid polymer-type fuel cell comprises a solid polymer electrolytic membrane composed of an ion exchange membrane (a polymer membrane having ion conductivity) such as perfluorocarbonsulfonic acid in which a sulfonic acid group is introduced into a fluorocarbon backbone such as a polytetrafluoroethylene backbone, two electrodes disposed on both sides of the electrolytic membrane, separators with grooves for supplying a gas such as hydrogen gas and oxygen gas to each electrode, and two current collectors disposed on backside of these separators.
Among these constituting members, the separator is required to have gas-imperviousness, low electrical resistance (electrical conductivity), resistance to sulfuric acid, and high mechanical strength. Traditionally, there is studied a method for molding a plate member made of titanium or graphite by a mechanical processing such as a cutting processing. However, this process lacks mass-productivity and it is difficult to carrying out on industrial scale.
Moreover, Japanese Patent Application Laid-Open No. 334927/1998 (JP-10-334927A) discloses a separator of a solid polymer-type fuel cell obtained by molding a resin composition which comprises a carbon powder, a thermosetting resin (phenolic resin, polyimide resin, epoxy resin, furan resin) by means of a resin molding process. However, the slow hardening of a phenolic resin used as the thermosetting resin results in the low productivity. For example, in Example 10 of the patent literature, post-hardening for 10 hours or more is required. Moreover, a gas such as water vapor generates as accompanied with hardening the phenolic resin so that warp forms in the hardened material and gas-imperviousness is deteriorated.
Further, Japanese Patent Application Laid-Open No. 267062/1992 (JP-4-267062A) discloses a gas separator for a fuel cell composed of stainless-steel or copper. However, although industrial productivity is high by the metal material, cell properties significantly lower due to deterioration of the material.